Asp.Net Web Api Odata V4 - Concurrency Checking

Question

Below code is generated from Wep Api Odata v4 scaffolding tool.

PUT Method

public IHttpActionResult Put([FromODataUri] string key, Delta<Product> patch)
{
    Validate(patch.GetEntity());

    if (!ModelState.IsValid)
    {
        return BadRequest(ModelState);
    }

    Product product = db.Products.Find(key);
    if (product == null)
    {
        return NotFound();
    }

    patch.Put(product);

    try
    {
        db.SaveChanges();
    }
    catch (DbUpdateConcurrencyException)
    {
        if (!ProductExists(key))
        {
            return NotFound();
        }
        else
        {
            throw;
        }
    }

    return Updated(product);
}

PATCH Method:

[AcceptVerbs("PATCH", "MERGE")]
public IHttpActionResult Patch([FromODataUri] string key, Delta<Product> patch)
{
    Validate(patch.GetEntity());

    if (!ModelState.IsValid)
    {
        return BadRequest(ModelState);
    }

    Product product = db.Products.Find(key);
    if (product == null)
    {
        return NotFound();
    }

    patch.Patch(product);

    try
    {
        db.SaveChanges();
    }
    catch (DbUpdateConcurrencyException)
    {
        if (!ProductExists(key))
        {
            return NotFound();
        }
        else
        {
            throw;
        }
    }

    return Updated(product);
}

Rowversion field in model

[Timestamp]
public byte[] RowVersion { get; set; }

Questions:

1. I need to implement concurrency check. How can I check optimistic concurrency in a Odata way (Using Etag)?
2. In above code DbUpdateConcurrencyException never thrown. Any reason?
3. There is a attribute called [ConcurrencyCheck] what is the use of it? Can I use this?

Providing a code sample will be highly appreciated!.

Answer 1

i solve this checking my self the concurrency fields because the patch or put dont does. This is my code where plato.TimeStamp is the [Timestamp] property.

   public async Task<IHttpActionResult> Put([FromODataUri] int key, Delta<Plato> patch)
    {
        Validate(patch.GetEntity());

        if (!ModelState.IsValid)
        {
            return BadRequest(ModelState);
        }

        Plato plato = await db.Platos.FindAsync(key);
        if (plato == null)
        {
            return NotFound();
        }
//Here save the current value in the DB
        string timeStamp = Convert.ToBase64String(plato.TimeStamp);
        patch.Put(plato);

        try
        {
//Here plato.TimeStamp is update from remote, must be equal to stored value
            if (timeStamp != Convert.ToBase64String(plato.TimeStamp))
            {
                throw new DbUpdateConcurrencyException();
            }
            await db.SaveChangesAsync();
        }
        catch (DbUpdateConcurrencyException)
        {
            if (!PlatoExists(key))
            {
                return NotFound();
            }
            else
            {
                throw;
            }
        }

        return Updated(plato);
    }